Bombus occidentalis
Encyclopedia
Bombus occidentalis is commonly known as the Western Bumble Bee. Bombus occidentalis is just one of the approximately thirty bumble bee species currently present in the western United States and western Canada. Bumble bees are considered to be true social insects as they have communal nest sites and share division of labor.
, carpenter
, cuckoo
, digger, stingless
, and orchid bees. Apidae are specialists for feeding on flowers and gathering nectar and pollen. Bumble bees belong to the order Hymenoptera (Greek origin hymen = membrane + ptera = wings). Hymenoptera are the only other order, besides Isoptera (termites), to have evolved complex social systems with division of labor. Aculeate Hymeoptera (certain wasps, bees, and ants) are the only insects that can sting. Unlike honey bees, bumble bees can sting repeatedly.
The color markings of bumble bees act as a warning to predators that they can sting if threatened. Bumble bees are covered with branched or feathered hair that pollen sticks to.
There are three types of bumble bees; queens (female), workers (female), drones (male). Although the queens and workers tend to have similar colorations and the same morphological (physical) features, the queens tend to be much larger in size
.
Bombus occidentalis workers have three main color variations.
colony. In Hymenoptera the females develop from fertilized eggs while the males develop from unfertilized eggs. Females control egg fertilization therefore regulating the sex ratio of offspring (haplodiploid method of sex determination).
have thirteen segments while the females have only twelve. Drones have no stinger
s. Additionally, the hind legs of the females tend to be wider and fatter with a pollen basket
often visible. Drones have thinner hind legs that do not have pollen baskets. Another clue to sexual identity among the Bombus occidentalis species is the time of year that they are being observed. Queens are the first to appear in the spring and then the workers appear. All Bombus occidentalis females can then be seen throughout the summer and into early fall. The drones will only appear in the late summer and early fall.
foragers. Because Bombus occidentalis do not depend on any one flower type, they are considered to be excellent pollinators. Bumble bees are also able to fly in cooler temperatures and lower light levels than many other bees. Additionally, bumble bees perform "buzz pollination
". This behavior is displayed when a bumble bee grabs the pollen producing structure of the flower in her jaws and vibrates her wing musculature causing vibrations that dislodge pollen that would have otherwise remained trapped in the flower's anthers. Tomato
es, peppers
, and cranberries
are some of the plants that require this type of pollination. For these reasons bumble bees are considered to be more effective pollinators than honey bees. Bombus occidentalis have been commercially reared to pollinate crops such as; alfalfa, avocado
s, apple
s, cherries
, blackberries
, cranberries, and blueberries
.
Workers collect nectar and store it in their stomach. Nectar is then converted into sugars and then regurgitated
at the nest. Pollen is collected and put into "pollen baskets" located on the hind legs. Nectar provides carbohydrates while pollen provides protein
.
, Washington, Alaska, Idaho
, Montana, western Nebraska
, western North Dakota
, western South Dakota
, Wyoming
, Utah
, Colorado
, northern Arizona
, and New Mexico
. Since 1998, Bombus occidentalis has been declining in population
. The areas of greatest decline have been reported in western and central California, western Oregon, western Washington, and British Columbia. From southern British Columbia to central California the species has nearly disappeared. The historic range was never systematically sampled.
Agricultural and urban development has resulted in bumble bee habitat becoming increasingly fragmented
. Size of population tends to decrease as inbreeding
becomes more prevalent. Scientific research has shown that as inbreeding increases genetic diversity
decreases along with increasing the risk of population decline.
Between 1992 and 1994, Bombus occidentalis and Bombus impatiens
were commercially reared for crop pollination, shipped to Europe
an rearing facilities and then shipped back. Bumble bee expert, Dr. Robbin Thorp, has hypothesized that the Bombus occidentalis decline is in part due to a disease acquired from a European bee while being reared in the same facility. North American bumble bees would have had no prior resistance to this pathogen. Upon returning to North America, affected bumble bees interacted and spread the disease to wild bumble bee populations. Bombus occidentalis and Bombus franklini were affected in the western United States. Bombus affinis and Bombus terricola were affected in the eastern United States. All four of these bumble bee species populations have been declining since the 90's. Additionally, these four bumble bee species are closely related and belong to the same subgenus; Bombus sensu stricto. Dr. Thorp has also hypothesized that the Bombus impatiens species may have been the carrier and that different bumble bee species may differ in their pathogen sensitivity.
Further support for Dr. Thorp's bumble bee hypothesis was shown in 2007 when the National Research Council
determined that the major cause of decline in native bumble bees appeared to be recently introduced non-native fungal and protozoan parasites, including Nosema bombi and Crithidia bombi.
General information
In the taxonomic hierarchy, all bumble bees belong to the genus Bombus within the family Apidae. Apidae also includes honeyHoney bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
, carpenter
Carpenter bee
Carpenter bees are large, hairy bees distributed worldwide. There are some 500 species of carpenter bee in 31 subgenera...
, cuckoo
Cuckoo bee
The term cuckoo bee is used for a variety of different bee lineages which have evolved the kleptoparasitic habit of laying their eggs in the nests of other bees, reminiscent of the behavior of cuckoo birds. The name is technically best applied to the apid subfamily Nomadinae...
, digger, stingless
Stingless bee
Stingless bees, sometimes called stingless honey bees or simply meliponines, are a large group of bees, comprising the tribe Meliponini . They belong in the family Apidae, and are closely related to common honey bees, carpenter bees, orchid bees and bumblebees...
, and orchid bees. Apidae are specialists for feeding on flowers and gathering nectar and pollen. Bumble bees belong to the order Hymenoptera (Greek origin hymen = membrane + ptera = wings). Hymenoptera are the only other order, besides Isoptera (termites), to have evolved complex social systems with division of labor. Aculeate Hymeoptera (certain wasps, bees, and ants) are the only insects that can sting. Unlike honey bees, bumble bees can sting repeatedly.
Description
Bumble bees are homometablous (complete metamorphosis).- Immature Stage
- GrubLarvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
-like - Well-developed head
- Chewing mouthparts
- Legless and eyeless
- Grub
- Adult Stage
- MaxillaMaxillaThe maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e and labium form proboscisProboscisA proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
for collecting nectar - Well-developed compound eyes
- TarsiArthropod legThe arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
usually 5 segments - Hind wings smaller than front wings and linked together by small hooks (hamuliHamulusHamus, Hamulus and words derived from them, are morphological or anatomical terms in various branches of biology. They describe structures functioning as, or in the form of, hooks or hooklets.-Derived terms:...
)
- Maxilla
The color markings of bumble bees act as a warning to predators that they can sting if threatened. Bumble bees are covered with branched or feathered hair that pollen sticks to.
There are three types of bumble bees; queens (female), workers (female), drones (male). Although the queens and workers tend to have similar colorations and the same morphological (physical) features, the queens tend to be much larger in size
.
Bombus occidentalis workers have three main color variations.
- 1st Color Variation - Found from northern CACaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, north to BCBritish ColumbiaBritish Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, east to southwest SaskatchewanSaskatchewanSaskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
and to MontanaMontanaMontana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
- Yellow hair on front part of thoraxThorax (insect anatomy)The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....
- 1st through basal section of 4th abdominalAbdomenIn vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
segments have black hair - Lower edge of the 4th and 5th abdominal segment are whitish
- 6th abdominal segment often has sparse, whitish hairs, but may still appear black
- Hair is entirely black on head
- Yellow hair on front part of thorax
- 2nd Color Variation - Found along the central coast in CA
- Yellow hair on the sides of the 2nd abdominal segment and all of 3rd abdominal segment
- Reddish brown hair on 5th abdominal segment
- 3rd Color Variation - Found from the Rocky MountainsRocky MountainsThe Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
to AlaskaAlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
- Yellow hair on the thorax behind the wings
- Yellow hair on the rear of the 2nd and all of the 3rd abdominal segments
Roles
- QueenQueen beeThe term queen bee is typically used to refer to an adult, mated female that lives in a honey bee colony or hive; she is usually the mother of most, if not all, the bees in the hive. The queens are developed from larvae selected by worker bees and specially fed in order to become sexually mature...
(female)- Lay eggs
- Fertilize eggs to produce more queens and workers (unfertilized eggs will become drones)
- Initiate new colonies
- Initial food collector and care of larvae until colony is established
- WorkersWorker beeA Worker bee is any female eusocial bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen, as well...
(sterile female)- Collect nectar and pollen
- Protect nest
- Feed queen, larvae, and drones (only until Fall)
- DronesDrone (bee)Drones are male honey bees. They develop from eggs that have not been fertilized, and they cannot sting, since the worker bee's stinger is a modified ovipositor .-Etymology:...
(male)- Mate with queen
- Cannot feed themselves
Life cycle
Bumble bees have an annual eusocialEusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
colony. In Hymenoptera the females develop from fertilized eggs while the males develop from unfertilized eggs. Females control egg fertilization therefore regulating the sex ratio of offspring (haplodiploid method of sex determination).
- Autumn - Queens and males mate, males die, queens find wintering site and enter diapauseDiapauseDiapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
(a form of hibernation) - Spring - Queens emerge from diapause and initiate new nest sites (often built in abandoned rodent burrows)
- Summer - Increased colony size where workers become the majority
- Late Summer - Reproductives produced and colony size decreases
Bumble Bee Species Identification
All insects have three main body parts; the head, thorax, and abdomen. Bumble bee species identification tends to refer to colorations on the abdominal segments. The abdominal segments are numbered from T1 to T6 (T7 if male) starting from the abdominal segment closest to the thorax and then working down. Bumble bee abdominal segments can be colored with black hair, orange/red hair, yellow hair, white hair, brown hair, mixed hair, or bald (no hair). Bumble bees facial hair color (black, yellow, or mixed) can also aid in the identification between species.Male or Female Determination
There are a few ways to determine the sex of Bombus occidentalis. The males (drones) have seven abdominal segments while the females (queens and workers) have only six. The drones' antennaeAntenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
have thirteen segments while the females have only twelve. Drones have no stinger
Stinger
-Biology:* Stinger, an organ or body part found in various animals that usually delivers some kind of venom.* Stinger , a minor neurological injury suffered by athletes.-Sports and entertainment:...
s. Additionally, the hind legs of the females tend to be wider and fatter with a pollen basket
Pollen basket
The pollen basket or corbicula is part of the tibia on the hind legs of the four related lineages of apid bees that used to comprise the family Apidae: the honey bees, bumblebees, stingless bees, and orchid bees...
often visible. Drones have thinner hind legs that do not have pollen baskets. Another clue to sexual identity among the Bombus occidentalis species is the time of year that they are being observed. Queens are the first to appear in the spring and then the workers appear. All Bombus occidentalis females can then be seen throughout the summer and into early fall. The drones will only appear in the late summer and early fall.
Behaviour
Bombus occidentalis are generalistGeneralist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
foragers. Because Bombus occidentalis do not depend on any one flower type, they are considered to be excellent pollinators. Bumble bees are also able to fly in cooler temperatures and lower light levels than many other bees. Additionally, bumble bees perform "buzz pollination
Buzz pollination
Sonication or buzz pollination is a technique used by some bees to release pollen which is more or less firmly held by the anthers, which makes pollination more efficient. The anther of buzz-pollinated species of plants is typically tubular, with an opening at only one end, and the pollen is inside...
". This behavior is displayed when a bumble bee grabs the pollen producing structure of the flower in her jaws and vibrates her wing musculature causing vibrations that dislodge pollen that would have otherwise remained trapped in the flower's anthers. Tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
es, peppers
Capsicum
Capsicum is a genus of flowering plants in the nightshade family, Solanaceae. Its species are native to the Americas where they have been cultivated for thousands of years, but they are now also cultivated worldwide, used as spices, vegetables, and medicines - and have become are a key element in...
, and cranberries
Cranberry
Cranberries are a group of evergreen dwarf shrubs or trailing vines in the subgenus Oxycoccus of the genus Vaccinium. In some methods of classification, Oxycoccus is regarded as a genus in its own right...
are some of the plants that require this type of pollination. For these reasons bumble bees are considered to be more effective pollinators than honey bees. Bombus occidentalis have been commercially reared to pollinate crops such as; alfalfa, avocado
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...
s, apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...
s, cherries
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....
, blackberries
Blackberry
The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...
, cranberries, and blueberries
Blueberry
Blueberries are flowering plants of the genus Vaccinium with dark-blue berries and are perennial...
.
Workers collect nectar and store it in their stomach. Nectar is then converted into sugars and then regurgitated
Regurgitation (digestion)
Regurgitation is the expulsion of material from the mouth, pharynx, or esophagus, usually characterized by the presence of undigested food or blood.Regurgitation is used by a number of species to feed their young...
at the nest. Pollen is collected and put into "pollen baskets" located on the hind legs. Nectar provides carbohydrates while pollen provides protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
.
Threats
- Spread of pests and diseases by commercial bumble bee industry
- Other pests and diseases
- Habitat destruction or alteration that may degrade, destroy, alter, fragment, and reduce their food supply or nest sites
- Pesticides and insecticides (ground bumble bees are particularly susceptible)
- Invasive species that may directly compete with native nectar and pollen plants
- Natural pest or predator population cycles
- Climate change
Status and Conservation
Due to their role as pollinators, loss of bumble bee populations can have far-ranging ecological impacts. Bombus occidentalis once had a wide range that included northern California, OregonOregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, Washington, Alaska, Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
, Montana, western Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
, western North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....
, western South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
, Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, northern Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. Since 1998, Bombus occidentalis has been declining in population
. The areas of greatest decline have been reported in western and central California, western Oregon, western Washington, and British Columbia. From southern British Columbia to central California the species has nearly disappeared. The historic range was never systematically sampled.
Agricultural and urban development has resulted in bumble bee habitat becoming increasingly fragmented
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
. Size of population tends to decrease as inbreeding
Inbreeding
Inbreeding is the reproduction from the mating of two genetically related parents. Inbreeding results in increased homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits. This generally leads to a decreased fitness of a population, which is...
becomes more prevalent. Scientific research has shown that as inbreeding increases genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
decreases along with increasing the risk of population decline.
Between 1992 and 1994, Bombus occidentalis and Bombus impatiens
Bombus impatiens
Bombus impatiens is the most often encountered bumblebee across much of eastern North America . Its range includes Ontario, Maine, Georgia, Kentucky, Maryland, New Jersey, New York, Pennsylvania, South Carolina, Virginia, West Virginia, south to Florida, west to Michigan, Illinois, Kansas, Missouri...
were commercially reared for crop pollination, shipped to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an rearing facilities and then shipped back. Bumble bee expert, Dr. Robbin Thorp, has hypothesized that the Bombus occidentalis decline is in part due to a disease acquired from a European bee while being reared in the same facility. North American bumble bees would have had no prior resistance to this pathogen. Upon returning to North America, affected bumble bees interacted and spread the disease to wild bumble bee populations. Bombus occidentalis and Bombus franklini were affected in the western United States. Bombus affinis and Bombus terricola were affected in the eastern United States. All four of these bumble bee species populations have been declining since the 90's. Additionally, these four bumble bee species are closely related and belong to the same subgenus; Bombus sensu stricto. Dr. Thorp has also hypothesized that the Bombus impatiens species may have been the carrier and that different bumble bee species may differ in their pathogen sensitivity.
Further support for Dr. Thorp's bumble bee hypothesis was shown in 2007 when the National Research Council
United States National Research Council
The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...
determined that the major cause of decline in native bumble bees appeared to be recently introduced non-native fungal and protozoan parasites, including Nosema bombi and Crithidia bombi.
External links
- Discover Life http://www.discoverlife.org/
- Bombus occidentalis Wanted Poster http://www.xerces.org/wp-content/uploads/2008/09/wanted_occidentalis.pdf
- Key to the Bombus of Evergreen http://academic.evergreen.edu/projects/ants/TESCBiota/kingdom/animalia/phylum/arthropoda/class/insecta/order/hymenoptera/family/Apidae/BOMBUS/key.htm